The present invention generally relates to the field of optical scanning, and more particularly to an optical scanning system which generates red, blue, and green light pulses in a repetitive sequence to create two and three dimensional images.
U.S. Pat. No. 5,854,613, entitled LASER BASED 3D VOLUMETRIC DISPLAY SYSTEM, describes a system for generating three dimensional images. The system employs red, green, and blue lasers. Each laser generates a laser beam that is subdivided into multiple laser beams that are directed through a separate deflection channel along its own optical axis. Each deflection channel includes both x- and y-acousto-optic beam deflectors or modulators for directing the subdivided laser beams to appropriate coordinates of the surface of a rotating reflective structure. However, multiple deflection channels make it difficult to maintain good color convergence over an extended period of time. Moreover, separate deflection channels increase both the cost and bulk of such systems. Therefore, a need exists for a color scanner system that may be used to create two and three dimensional color images that uses only one deflection channel.
The present invention provides a sequential color scanner capable of generating both two and three dimensional, moving color images with only one x- and y-deflection channel. The system includes first, second, and third optical signal generators for generating a first, second, and third optical signal, respectively. Each optical signal is characterized by one of the three primary colors, blue, green, and red, although not necessarily in that order. The first optical signal is generated along an optical axis. First and second beam combiners direct the second and third optical signals, respectively, along the optical axis. A first optical deflector deflects the optical signals in a first plane, and a second optical deflector for deflecting the optical signals in a second plane that is orthogonal to the first plane. First, second, and third modulators modulate the intensity of the first, second, and third optical signals, respectfully, under the supervision of a controller so that the optical signals are generated in a pulsed, interlaced, and repeating sequence in accordance with an index counted by an index counter implemented in the controller. The controller also supervises modulation of the first and second optical deflectors for directing the light signals to predetermined coordinates, and generates a clock signal having a periodicity P. The repeating sequence includes a first pulse of the first optical signal having a duration of (wP-xcfx84), a second pulse of the second optical signal having a duration of (yP-xcfx84), and a third pulse of the third optical signal having a duration of (zP-xcfx84), where w, y, and z are positive integers, and r represents a time delay. The time delay xcfx84 between optical signals is used to enhance the sharpness of the image by assuring that the optical deflectors modulate only one light signal at a time.
An important advantage of the invention is that it only requires one optical channel for deflecting each of the red, green, and blue pulsed optical signals. Another important advantage of the invention is that if the intensities of the first, second, and third light signals generated by the light signal generators are not equal, the invention may be configured to make the durations of the pulsed light signals different so that the light signals reflected off a reflecting structure appear to be equal.
These and other advantages of the invention will become more apparent upon review of the accompanying drawings and specification, including the claims.